Low Field Magnetic Resonance Imaging
We are developing a SQUID system for Magnetic Resonance Imaging (MRI) at low magnetic fields.
The system is suitable for samples of a few centimeter’s size. The sample is either pre-polarized by a strong permanent magnet and transported to the measurement site inside the magnetically shielded room, or it is magnetized in situ in a solenoid which creates the polarizing field Bp. The coil for the tipping field Brf is wound outside the Bp solenoid. A Helmholtz coil pair generates the measurement field Bm which is applied perpendicular to Bp. The gradient field Gzz is produced by a Maxwell coil pair. The other two gradient field components, Gzx and Gzy, are generated by pairs of planar grid coils, respectively. The relaxation signal from the sample is measured by a liquid nitrogen cooled SQUID sensor located inside a fiberglass cryostat.
A more detailed description of our Low Field Nuclear Magnetic Resonance (NMR) / Magnetic Resonance Imaging (MRI) system and its performance is found in our publication Dong et al., IEEE Trans. Appl. Supercond. 21, 509 (2011).